cleanup: fix header include guards

cleanup: fix header include guards

...to resolve the following linter errors:

    $ tools/check-include-guards.sh
    ...
    src/bindings/python/bt2/bt2/native_bt_log_and_append_error.hpp: In `#ifndef BABELTRACE_BINDINGS_PYTHON_BT2_BT2_NATIVE_BT_LOG_AND_APPEND_ERROR_H` include guard line: expecting `#ifndef BABELTRACE_BINDINGS_PYTHON_BT2_BT2_NATIVE_BT_LOG_AND_APPEND_ERROR_HPP`
    ...
    src/bindings/python/bt2/bt2/native_bt_bt2_objects.hpp: In `#ifndef BABELTRACE_BINDINGS_PYTHON_BT2_BT2_NATIVE_BT_BT2_OBJECTS_H` include guard line: expecting `#ifndef BABELTRACE_BINDINGS_PYTHON_BT2_BT2_NATIVE_BT_BT2_OBJECTS_HPP`
    ...

These errors were introduced in commit
c217058f798d ("bt2: some more .h -> .hpp") where the headers were
converted to .hpp but the include guards were not updated.

Change-Id: I2f422c3c8ab1a5ad1f3854fb90ca7163d61f6b04
Signed-off-by: Erica Bugden <ebugden@efficios.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/13528
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>
Reviewed-by: Simon Marchi <simon.marchi@efficios.com>